Heterogeneity in transmissibility and shedding SARS-CoV-2 via droplets and aerosols

Chen, Paul Z.; Bobrovitz, Niklas; Premji, Zahra; Koopmans, Marion; Fisman, David N.; Gu, Frank

doi:10.7554/elife.65774

Cited by 133 publications

(107 citation statements)

References 136 publications

(249 reference statements)

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“…Symptomatic COVID-19 patients are more contagious regardless of the presence of close contacts [ 29 ], but asymptomatic patients run higher risks of spreading the virus to the general populace as they move around [ 30 ]. Asymptomatic infections are estimated to be 20% [ 31 ].…”

Section: Discussion: Lessons Learned and Recommendationsmentioning

confidence: 99%

The COVID-19 Pandemic Situation in Malaysia: Lessons Learned from the Perspective of Population Density

Teh

Ling

et al. 2021

IJERPH

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This paper attempts to ascertain the impacts of population density on the spread and severity of COVID-19 in Malaysia. Besides describing the spatio-temporal contagion risk of the virus, ultimately, it seeks to test the hypothesis that higher population density results in exacerbated COVID-19 virulence in the community. The population density of 143 districts in Malaysia, as per data from Malaysia’s 2010 population census, was plotted against cumulative COVID-19 cases and infection rates of COVID-19 cases, which were obtained from Malaysia’s Ministry of Health official website. The data of these three variables were collected between 19 January 2020 and 31 December 2020. Based on the observations, districts that have high population densities and are highly inter-connected with neighbouring districts, whether geographically, socio-economically, or infrastructurally, tend to experience spikes in COVID-19 cases within weeks of each other. Using a parametric approach of the Pearson correlation, population density was found to have a moderately strong relationship to cumulative COVID-19 cases (p-value of 0.000 and R2 of 0.415) and a weak relationship to COVID-19 infection rates (p-value of 0.005 and R2 of 0.047). Consequently, we provide several non-pharmaceutical lessons, including urban planning strategies, as passive containment measures that may better support disease interventions against future contagious diseases.

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Section: Discussion: Lessons Learned and Recommendationsmentioning

confidence: 99%

The COVID-19 Pandemic Situation in Malaysia: Lessons Learned from the Perspective of Population Density

Teh

Ling

et al. 2021

IJERPH

View full text Add to dashboard Cite

show abstract

“…Aerosol transmission, direct contact transmission, and fomite transmission have been experimentally demonstrated in multiple animal models [ 49 , 338 – 343 ]. Furthermore, studies in non-human primates, and confirmed in humans, demonstrate that infected individuals exhale infectious aerosols, but this is highly variable across individuals and activities [ 344 , 345 ].…”

Section: Main Textmentioning

confidence: 99%

“…Highquality research is needed to better understand these aspects and attempt to estimate the relative contribution and importance of the transmission routes of SARS-CoV-2. However, this is challenging because of the complexities in transmission [49], including the fact that respiratory particles containing infectious SARS-CoV-2 are highly variable in different individuals and with different activities [344,345].…”

Section: Unknowns In Sars-cov-2 Transmissionmentioning

confidence: 99%

COVID-19 false dichotomies and a comprehensive review of the evidence regarding public health, COVID-19 symptomatology, SARS-CoV-2 transmission, mask wearing, and reinfection

et al. 2021

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Scientists across disciplines, policymakers, and journalists have voiced frustration at the unprecedented polarization and misinformation around coronavirus disease 2019 (COVID-19) pandemic. Several false dichotomies have been used to polarize debates while oversimplifying complex issues. In this comprehensive narrative review, we deconstruct six common COVID-19 false dichotomies, address the evidence on these topics, identify insights relevant to effective pandemic responses, and highlight knowledge gaps and uncertainties. The topics of this review are: 1) Health and lives vs. economy and livelihoods, 2) Indefinite lockdown vs. unlimited reopening, 3) Symptomatic vs. asymptomatic severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection, 4) Droplet vs. aerosol transmission of SARS-CoV-2, 5) Masks for all vs. no masking, and 6) SARS-CoV-2 reinfection vs. no reinfection. We discuss the importance of multidisciplinary integration (health, social, and physical sciences), multilayered approaches to reducing risk (“Emmentaler cheese model”), harm reduction, smart masking, relaxation of interventions, and context-sensitive policymaking for COVID-19 response plans. We also address the challenges in understanding the broad clinical presentation of COVID-19, SARS-CoV-2 transmission, and SARS-CoV-2 reinfection. These key issues of science and public health policy have been presented as false dichotomies during the pandemic. However, they are hardly binary, simple, or uniform, and therefore should not be framed as polar extremes. We urge a nuanced understanding of the science and caution against black-or-white messaging, all-or-nothing guidance, and one-size-fits-all approaches. There is a need for meaningful public health communication and science-informed policies that recognize shades of gray, uncertainties, local context, and social determinants of health.

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“…Occasionally multiple infections occur on a single flight [ 32 ]; but the majority of potential exposures on planes lead to no transmission [ 33 ]. These considerations point to COVID-19 transmission being highly heterogeneous, or “overdispersed”, a phenomenon with a building body of evidence [ 30 , 34 – 36 ].…”

Section: Introductionmentioning

confidence: 99%

COVID-19 in schools: Mitigating classroom clusters in the context of variable transmission

Tupper

Colijn

2021

PLoS Comput Biol

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Widespread school closures occurred during the COVID-19 pandemic. Because closures are costly and damaging, many jurisdictions have since reopened schools with control measures in place. Early evidence indicated that schools were low risk and children were unlikely to be very infectious, but it is becoming clear that children and youth can acquire and transmit COVID-19 in school settings and that transmission clusters and outbreaks can be large. We describe the contrasting literature on school transmission, and argue that the apparent discrepancy can be reconciled by heterogeneity, or “overdispersion” in transmission, with many exposures yielding little to no risk of onward transmission, but some unfortunate exposures causing sizeable onward transmission. In addition, respiratory viral loads are as high in children and youth as in adults, pre- and asymptomatic transmission occur, and the possibility of aerosol transmission has been established. We use a stochastic individual-based model to find the implications of these combined observations for cluster sizes and control measures. We consider both individual and environment/activity contributions to the transmission rate, as both are known to contribute to variability in transmission. We find that even small heterogeneities in these contributions result in highly variable transmission cluster sizes in the classroom setting, with clusters ranging from 1 to 20 individuals in a class of 25. None of the mitigation protocols we modeled, initiated by a positive test in a symptomatic individual, are able to prevent large transmission clusters unless the transmission rate is low (in which case large clusters do not occur in any case). Among the measures we modeled, only rapid universal monitoring (for example by regular, onsite, pooled testing) accomplished this prevention. We suggest approaches and the rationale for mitigating these larger clusters, even if they are expected to be rare.

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Heterogeneity in transmissibility and shedding SARS-CoV-2 via droplets and aerosols

Cited by 133 publications

References 136 publications

The COVID-19 Pandemic Situation in Malaysia: Lessons Learned from the Perspective of Population Density

The COVID-19 Pandemic Situation in Malaysia: Lessons Learned from the Perspective of Population Density

COVID-19 false dichotomies and a comprehensive review of the evidence regarding public health, COVID-19 symptomatology, SARS-CoV-2 transmission, mask wearing, and reinfection

COVID-19 in schools: Mitigating classroom clusters in the context of variable transmission

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